Techniques have already been proposed in which dampers are embedded in walls of a building or the like to provide the walls with a vibration damping structure to thereby provide the overall building with a vibration damping structure.
A cylinder-rod type damper having a cylinder and a rod passed through the cylinder as a damper of this type is used such that one end portion side of the cylinder is fixed to a column or a horizontal member in one corner portion of a wall space defined by left and right columns and upper and lower horizontal members, and one end portion side of the rod projecting from the cylinder is fixed to the column or horizontal member in another corner portion on a diagonal line with respect to the one corner portion in the wall space.
Incidentally, since it is necessary for such a damper to extend or contract and swing with respect to the columns or the horizontal members at the respective corner portions when the building shakes due to an earthquake and the wall space undergoes deformation, the one end portion side of the cylinder and the one end portion side of the rod are respectively fixed swingably to the columns or the horizontal members at the respective corner portions by means of swivel fittings or the like. However, the use of such swivel fittings or the like entails a rise in the cost. Moreover, there is a possibility of abnormal noise being generated due to the sliding in swinging, and there is a possibility of impairing the damping effect due to looseness in installation.
In addition, with the cylinder-rod type damper, if the cylinder and the rod are made long in an attempt to generate a large damping force so as to efficiently damp vibrations due to an earthquake at an early period, the occupying space in the axial direction becomes large in the installation. Moreover, a thick cylinder and a large rod are inevitably used so as not to cause deflection or the like, so that the weight becomes extremely large. On the other hand, if the gap between the cylinder and the rod is made small, the cylinder and the rod come into contact with each other in connection with the dimensional accuracy in the manufacture of the cylinder and the rod. In some cases, the rod becomes unable to move in the axial direction with respect to the cylinder.
The present invention has been devised in view of the above-described aspects, and its object is to provide a damper which with a simple construction can be installed in a wall in the form of a diagonal brace or installed on a column in such a manner as to extend substantially in parallel to the column in a substantially vertical direction, and which is capable of reducing the cost, and does not produce abnormal noise in shaking, as well as a vibration damping structure using the same.
Another object of the present invention is to provide a damper which is capable of generating a large damping force without enlarging the occupying space in the axial direction and the weight and without causing an undesirable situation such as contact between the cylinder and the rod, as well as a vibration damping structure using the same.